I solved this problem theoretically and checked ability of a jump by counting the discriminant of square equation. I got WA on tests 30-32 using floating point numbers and trying to find good precision (type double in C) and rewrote my program using long integer type (long long) with no precisions. The first thing I noticed is that I got WA on test 20 when I say that jump is possible if D>=0. If I check D>0, I get WA on test 32. I'm sure it's not correct, because if D=0 exactly jump is still possible. I thought the problem could be in overflowing. Despite long long must be enough, I rewrote the program in Python 3 to avoid overflowing for sure and nothing changed. So I think I am right and there are wrong tests. I can show my source code if needed.